ClassNotFoundException with URLClassLoader in classes.jar (java.net package)

eclipse classnotfoundexception urlclassloader
tom picture tom · Dec 1, 2010 · Viewed 7.5k times · Source

On Eclipse Galileo, got the following ClassNotFoundException when doing Debug As/Web Application. But works just fine when doing Run As/Web Application.

I was given message that "The source attachment does not contain the source for the file URLClassLoader.class. You can change the source attachment by clicking the Change Attached Source below:"

In the project window, it seems that the URLClassLoader class is from Java.net package, which is from /System/Library/Frameworks/JavaVM.framework/Versions/1.6.0/Classes/classes.jar.

I found the jar on the machine, what else I am missing? why it's debug only issue?

Could it be possible that the JRE system library that I have on my iMac 10.6.5 machine is outdated? Or somehow install/unstall of some jar/package caused the issue?

This is what I have - JRE System Library [JVM 1.6.0 (MacOS X Default)] - would update it help fixing the issue? but how to get it updated?

Please help!

com.google.appengine.tools.development.DevAppServerMain at localhost:57873 
 Thread [main] (Suspended (exception ClassNotFoundException)) 
  Launcher$ExtClassLoader(URLClassLoader).findClass(String) line: 207 
  Launcher$ExtClassLoader.findClass(String) line: 229 
  Launcher$ExtClassLoader(ClassLoader).loadClass(String, boolean) line: 307 
  Launcher$AppClassLoader(ClassLoader).loadClass(String, boolean) line: 296 
  Launcher$AppClassLoader.loadClass(String, boolean) line: 301 
  Launcher$AppClassLoader(ClassLoader).loadClass(String) line: 248 
  InstrumentationImpl.loadClassAndStartAgent(String, String, String) line: 280 
  InstrumentationImpl.loadClassAndCallPremain(String, String) line: 338 
/System/Library/Frameworks/JavaVM.framework/Versions/1.6.0/Home/bin/java (Nov 30, 2010 9:40:41 PM)

Answer

user591593 picture user591593 · Aug 4, 2011

Perhaps you need to install JDK which has complete sources? Refer to Apple website to download the latest JDK, might need an Apple ID.

After that change eclipse's java runtime accordingly to use the new installed JDK:

enter image description here

And re-build your project: Project -> Source -> Clean-up

Related questions

JUNIT Test class in Eclipse - java.lang.ClassNotFoundException

I'm trying to run my junit test (to verify that a properties file loads correctly) but I get ClassNotFoundException although the class is there and all required libraries are there too. Here it is the error I get : Class not …

Read More
How to install JDBC driver in Eclipse web project without facing java.lang.ClassNotFoundexception

There is a VERY similar question to mine but in my case I don't have any duplicate jars in my build path, so the solution does not work for me. I've searched google for a couple of hours now, but …

Read More
ClassNotFoundException oracle.jdbc.driver.OracleDriver only in servlet, using Eclipse

The code below fails on the line: Class.forName("oracle.jdbc.driver.OracleDriver"); with the error: java.lang.ClassNotFoundException: oracle.jdbc.driver.OracleDriver The two printlns print: Wed_Jun_22_11:18:51_PDT_2005 false This makes me think the class exists and can …

Read More